Update pow() tests to check for both errno==EDOM _and_ result==Nan, and

document why this happens.  Remove exp() errno check because not needed.

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 441f766f0ba4dd38b85377de930fa2010b100a1b..128f147debd342b9f440d3cc9e54ebb7b360a8d0 100644 (file)
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.138 2007/01/03 19:34:23 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.139 2007/01/03 22:05:00 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1440,17 +1440,24 @@ dpow(PG_FUNCTION_ARGS)
 
    /*
     * pow() sets errno only on some platforms, depending on whether it
-    * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, and some return Nan,
-    * so we check and set result properly.
+    * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, so we try to avoid
+    * using errno.  However, some platform/CPU combinations return
+    * errno == EDOM and result == Nan, so we have to check for that and
+    * set result properly.  For example, Linux on Pentium, pre-Xeon
+    * hardware returns EDOM/Nan for (-1) ^ 1e19, but (-1) ^ 1e18 retuns
+    * 1 -- basically a negative base raised to a very high power causes
+    * it on some CPUs.
     */
    errno = 0;
    result = pow(arg1, arg2);
-   if (errno == ERANGE || isnan(result))
+   if (errno == EDOM && isnan(result))
    {
        if ((fabs(arg1) > 1 && arg2 >= 0) || (fabs(arg1) < 1 && arg2 < 0))
            result = (arg1 >= 0) ? get_float8_infinity() : -get_float8_infinity();
-       else
+       else if (fabs(arg1) != 1)
            result = 0;
+       else
+           result = 1;
    }
    
    CHECKFLOATVAL(result, isinf(arg1) || isinf(arg2), arg1 == 0);
@@ -1467,20 +1474,7 @@ dexp(PG_FUNCTION_ARGS)
    float8      arg1 = PG_GETARG_FLOAT8(0);
    float8      result;
 
-   /*
-    * exp() sets errno only on some platforms, depending on whether it
-    * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, and some return Nan,
-    * so we check and set result properly.
-    */
-   errno = 0;
    result = exp(arg1);
-   if (errno == ERANGE || isnan(result))
-   {
-       if (arg1 >= 0)
-           result = get_float8_infinity();
-       else
-           result = 0;
-   }
 
    CHECKFLOATVAL(result, isinf(arg1), false);
    PG_RETURN_FLOAT8(result);